Preheat oven to 400°F (200°C). Lightly grease a 9×13-inch baking dish with butter or cooking spray.

Slice each chicken breast in half horizontally to create 4 cutlets. Pound gently to even thickness.

Marinate chicken in a bowl with 1 tablespoon olive oil, garlic, Italian seasoning, salt, and pepper. Cover and refrigerate for 15–30 minutes.

Heat remaining olive oil in a skillet over medium heat. Add spinach and sauté until wilted, about 2–3 minutes. Let cool slightly.

In a medium bowl, beat cream cheese until smooth. Mix in spinach, 1/2 cup mozzarella, and Parmesan (if using).

Optional: Sear chicken for 1–2 minutes per side for extra flavor. Arrange cutlets in prepared baking dish.

Spread the cream cheese mixture over chicken. Top with remaining mozzarella.

Bake for 20–30 minutes, or until chicken reaches 165°F internally and cheese is golden and bubbly.

Let rest 5 minutes, then serve warm.